The magnitude 6.7 Northridge earthquake in January 1994 killed 57 people and injured about 8,700.

The rate of heart attacks in the Bay area remained largely unchanged in the week after the 7.1 Loma Prieta earthquake in 1989 but myocardial infarction jumped 35 percent in Southern California following the 6.7 Northridge shaker in 1994, says a new study published in the journal Lancet.

The finding was based on a review of 123 scientific papers published from 1990 to 2010. Each study involved at least 50 patients.

The study, first reported by Medscape Medical News, involves a global look at morbidity and mortality linked to earthquakes. The researchers apparently didn't pinpoint why the rate of heart attacks in Southern California rose while they remained flat in the Bay area. But the study suggests there can be significant regional differences in the fall out from a large quake.

The Medscape story also highlights these findings from the Lancet study:

As people are displaced from their damaged homes, overcrowding in shelters with poor sanitation also can trigger infectious disease outbreaks and sepsis, which increases mortality 2.5-fold. However, the reviewers note that the role of corpses in such outbreaks tends to be exaggerated, except in the transmission of cholera.

Earthquakes often trigger psychiatric conditions, particularly depression (which may affect from 6% to 72% of the exposed population) and posttraumatic stress disorder (which may affect from 3.3% to 81% of the exposed population). Suicidal ideation was reported in 17% of the population after the 1999 Turkey earthquake.